The present invention is directed to a positioning work stop and more particularly to a positioning work stop for use with a machine tool in performing a precision machining operation and which operates to allow an operator to place a work piece in its proper position for machining and further operates to retract out of contact with the work piece to create a gap between the positioning work stop and the work piece to allow for uninterrupted machining.
Computerized numerical controls (CNC) and other well-known machine tools are used to perform various machining operations. Before a machining operation can be performed, the work piece to be machined must be properly placed and held in a mounting fixture for positioning the work piece at a desired location relative to the machining tool. This is particularly important when the machining process is being performed on a CNC machine where the position of the work piece must align with the zero reference point programmed into the computer controls. A number of conventional positioning stops have been developed to accomplish the task of ensuring that the work piece is properly positioned.
Most such positioning work stops are relatively simple, manually operated devices whereby the machine operator installs the stop at a desired location and orientation, and sets the stop mechanism. When the work piece is placed in the mounting fixture and the surface makes contact with the stop, the machine operator knows that the work piece is in its proper position for machining. Such stops are typically rigid and if a gap is needed, such as during a cutting operation to allow a portion of a cut to fall away from the work piece such as to prevent the cutting blade from binding, a spacer is often needed to be inserted between the work piece and the stop. The spacer then must be held in place by a holding apparatus. Unfortunately, the use of such spacers is time consuming and work pieces often are jarred during installation of the spacer and may no longer be in its proper position for machining. This is a significant problem when machining highly precision parts. Further, if the work piece shifts out of position it is often not noticed by the operator and the machining continues to be performed. This shifting causes the work piece to be cut or machined out of specification resulting in the work piece being scrapped or reworked. Further, this requires each work piece to be carefully inspected after the machining operation thereby significantly increasing the manufacturing time and cost of operation. Another difficulty with the use of spacers is that typically after the machining operation has started, the operator must hold the work piece in one hand and install the spacer with the other hand ensuring that it is held flat against the work piece while at the same time tightening a holding apparatus to maintain the spacer in position. This process is again time consuming and can result in the work piece being moved slightly out of position.
Accordingly, there is a need for a positioning work stop that can be used with conventional machining apparatus and operates to ensure that the work piece is in its proper position for machining and reduces the likelihood that the work piece will shift out of its proper position. Further, a need exists for a positioning work stop that allows a gap to be easily created between the positioning work stop and the work piece during certain machining operations without interruption of the machining process.